Despite strong evidence that diet, exercise, and weight loss can lead to clinically important improvement in risk factors for both micro- and macrovascular disease in people with type 2 diabetes, barriers at the patient, clinician, and health system level have prevented the translation of these findings into practice. The proposed translational study, Improving Control with Activity and Nutrition (ICAN) is a partnership between the University of Virginia and Southern Health Systems, a health plan with enrollees throughout Virginia, to demonstrate that clinically proven lifestyle interventions can be implemented and maintained in settings more typical of those in which a majority of Americans receive care. The proposed study is a two arm randomized clinical trial of the ability of lifestyle case management interventions to improve glycemic control, reduce macro- and microvascular disease risk factors, support health-promoting diet and exercise habits, improve quality of life, and reduce the use of high intensity health care venues, among health plan enrollees with type 2 diabetes who are obese. Participants will be randomly assigned to one of two conditions: 1) the lifestyle case management group, which will receive 6 months of theory-based and demonstrated intensive lifestyle intervention, followed by 36 months of lifestyle case management designed to help participants maintain or enhance their diet and exercise habits; 2) the lifestyle intervention group, which will receive the same intense 6 month intervention, but will not receive ongoing guidance after 6 months (the "lifestyle intervention" group). Both groups will be followed for 42 months. Primary study outcomes are glycemic control (HbA1c), lipid profiles, diet and exercise behavior, and health care utilization; a process evaluation will focus on acceptance of the project by participants and physicians, as well as mechanisms through which the intervention influences behavior change. We hypothesize that the lifestyle case management intervention will result in improved glycemic control and risk factor status, greater maintenance of changes in diet and exercise, and decreased health care utilization, compared to the lifestyle intervention group. The project complements existing primary care for type 2 diabetes; patients will continue to be treated by their regular physicians during the trial. Results will be immediately applicable to a majority of health plans and practices in the U.S.